The present invention is generally related to flow restrictors.
Fuel metering units, pneumatic systems, and lubrication systems in gas turbine engines commonly use a flow restrictor to restrict and regulate the flow of fluids through fluid passages. A flow restrictor is generally a cylindrical tube disposed inside a fluid passage and includes an internal profile that reduces the diameter of the flow area in the fluid passage, similar to a venturi tube. Some flow restrictors are installed inside the fluid passage through an interference fit while others are installed through intricate retaining systems.
If the flow restrictor and retaining system are misassembled inside the fluid passage, the retaining system may fail and permit the flow restrictor to shift and move inside the fluid passage. Engine vibrations, over time, may also loosen the interference fit or retaining system between the flow restrictor and the fluid passage, thereby allowing the flow restrictor to shift and move within the fluid passage. If the flow restrictor shifts or moves inside the fluid passage, the flow restrictor could undesirably block inlet and outlet orifices connected to the fluid passage. The flow restrictor could also move to a position inside the fluid passage where the flow restrictor is no longer operable in restricting or regulating the flow of fluid inside the fluid passage. This problem has been overcome in the past by permanently fixing the flow restrictor inside the fluid line through the use of an adhesive or braze. However, permanently fixing the flow restrictor inside the fluid passage prevents an operator from easily replacing the restrictor in the future should the operator wish to subsequently adjust the flow in the fluid passage by installing a flow restrictor with a larger or smaller interior profile.